using System;
using System.Collections.Generic;
using System.Text;

namespace AninToBVH
{
    /// <summary>
    /// Reads in a byte array of an Animation Asset created by the SecondLife(tm) client.
    /// </summary>
    public class myBinBVHAnimationReader
    {
        /// <summary>
        /// Rotation Keyframe count (used internally)
        /// </summary>
        private int rotationkeys;
        
        /// <summary>
        /// Position Keyframe count (used internally)
        /// </summary>
        private int positionkeys;

        public UInt16 unknown0; // Always 1
        public UInt16 unknown1; // Always 0

        /// <summary>
        /// Animation Priority
        /// </summary>
        public int Priority;

        /// <summary>
        /// The animation length in seconds.
        /// </summary>
        public Single Length;

        /// <summary>
        /// Expression set in the client.  Null if [None] is selected
        /// </summary>
        public string ExpressionName; // "" (null)

        /// <summary>
        /// The time in seconds to start the animation
        /// </summary>
        public Single InPoint;

        /// <summary>
        /// The time in seconds to end the animation
        /// </summary>
        public Single OutPoint;

        /// <summary>
        /// Loop the animation
        /// </summary>
        public bool Loop;

        /// <summary>
        /// Meta data. Ease in Seconds.
        /// </summary>
        public Single EaseInTime;

        /// <summary>
        /// Meta data. Ease out seconds.
        /// </summary>
        public Single EaseOutTime;

        /// <summary>
        /// Meta Data for the Hand Pose
        /// </summary>
        public uint HandPose;

        /// <summary>
        /// Number of joints defined in the animation
        /// </summary>
        public uint JointCount;


        /// <summary>
        /// Contains an array of joints
        /// </summary>
        public binBVHJoint[] joints;

        /// <summary>
        /// Searialize an animation asset into it's joints/keyframes/meta data
        /// </summary>
        /// <param name="animationdata"></param>
        public myBinBVHAnimationReader(byte[] animationdata)
        {
            int i = 0;
            if (!BitConverter.IsLittleEndian)
            {
                unknown0 = Utils.BytesToUInt16(EndianSwap(animationdata, i, 2)); i += 2; // Always 1
                unknown1 = Utils.BytesToUInt16(EndianSwap(animationdata, i, 2)); i += 2; // Always 0
                Priority = Utils.BytesToInt(EndianSwap(animationdata, i, 4)); i += 4;
                Length = Utils.BytesToFloat(EndianSwap(animationdata, i, 4), 0); i += 4;
            }
            else
            {
                unknown0 = Utils.BytesToUInt16(animationdata, i); i += 2; // Always 1
                unknown1 = Utils.BytesToUInt16(animationdata, i); i += 2; // Always 0
                Priority = Utils.BytesToInt(animationdata, i); i += 4;
                Length = Utils.BytesToFloat(animationdata, i); i += 4;
            }
            ExpressionName = ReadBytesUntilNull(animationdata, ref i);
            if (!BitConverter.IsLittleEndian)
            {
                InPoint = Utils.BytesToFloat(EndianSwap(animationdata, i, 4), 0); i += 4;
                OutPoint = Utils.BytesToFloat(EndianSwap(animationdata, i, 4), 0); i += 4;
                Loop = (Utils.BytesToInt(EndianSwap(animationdata, i, 4)) != 0); i += 4;
                EaseInTime = Utils.BytesToFloat(EndianSwap(animationdata, i, 4), 0); i += 4;
                EaseOutTime = Utils.BytesToFloat(EndianSwap(animationdata, i, 4), 0); i += 4;
                HandPose = Utils.BytesToUInt(EndianSwap(animationdata, i, 4)); i += 4; // Handpose?

                JointCount = Utils.BytesToUInt(animationdata, i); i += 4; // Get Joint count
            }
            else
            {
                InPoint = Utils.BytesToFloat(animationdata, i); i += 4;
                OutPoint = Utils.BytesToFloat(animationdata, i); i += 4;
                Loop = (Utils.BytesToInt(animationdata, i) != 0); i += 4;
                EaseInTime = Utils.BytesToFloat(animationdata, i); i += 4;
                EaseOutTime = Utils.BytesToFloat(animationdata, i); i += 4;
                HandPose = Utils.BytesToUInt(animationdata, i); i += 4; // Handpose?

                JointCount = Utils.BytesToUInt(animationdata, i); i += 4; // Get Joint count
            }
            joints = new binBVHJoint[JointCount];

            // deserialize the number of joints in the animation.
            // Joints are variable length blocks of binary data consisting of joint data and keyframes
            for (int iter = 0; iter < JointCount; iter++)
            {
                binBVHJoint joint = readJoint(animationdata, ref i);
                joints[iter] = joint;
            }
        }

        private byte[] EndianSwap(byte[] arr, int offset, int len)
        {
            byte[] bendian = new byte[offset + len];
            Buffer.BlockCopy(arr, offset, bendian, 0, len);
            Array.Reverse(bendian);
            return bendian;
        }
        /// <summary>
        /// Variable length strings seem to be null terminated in the animation asset..    but..   
        /// use with caution, home grown.
        /// advances the index.
        /// </summary>
        /// <param name="data">The animation asset byte array</param>
        /// <param name="i">The offset to start reading</param>
        /// <returns>a string</returns>
        public string ReadBytesUntilNull(byte[] data, ref int i)
        {
            char nterm = '\0'; // Null terminator
            int endpos = i;
            int startpos = i;

            // Find the null character
            for (int j = i; j < data.Length; j++)
            {
                char spot = Convert.ToChar(data[j]);
                if (spot == nterm)
                {
                    endpos = j;
                    break;
                }
            }

            // if we got to the end, then it's a zero length string
            if (i == endpos)
            {
                // advance the 1 null character
                i++;
                return string.Empty;
            }
            else
            {
                // We found the end of the string
                // append the bytes from the beginning of the string to the end of the string
                // advance i
                byte[] interm = new byte[endpos - i];
                for (; i < endpos; i++)
                {
                    interm[i - startpos] = data[i];
                }
                i++;  // advance past the null character

                return Utils.BytesToString(interm);
            }
        }

        /// <summary>
        /// Read in a Joint from an animation asset byte array
        /// Variable length Joint fields, yay!
        /// Advances the index
        /// </summary>
        /// <param name="data">animation asset byte array</param>
        /// <param name="i">Byte Offset of the start of the joint</param>
        /// <returns>The Joint data serialized into the binBVHJoint structure</returns>
        public binBVHJoint readJoint(byte[] data, ref int i)
        {

            binBVHJointKey[] positions;
            binBVHJointKey[] rotations;

            binBVHJoint pJoint = new binBVHJoint();

            /*
                109
                84
                111
                114
                114
                111
                0 <--- Null terminator
            */

            pJoint.Name = ReadBytesUntilNull(data, ref i); // Joint name

            /* 
                 2 <- Priority Revisited
                 0
                 0
                 0
            */

            /* 
                5 <-- 5 keyframes
                0
                0
                0
                ... 5 Keyframe data blocks
            */

            /* 
                2 <-- 2 keyframes
                0
                0
                0
                ..  2 Keyframe data blocks
            */
            if (!BitConverter.IsLittleEndian)
            {
                pJoint.Priority = Utils.BytesToInt(EndianSwap(data, i, 4)); i += 4; // Joint Priority override?
                rotationkeys = Utils.BytesToInt(EndianSwap(data, i, 4)); i += 4; // How many rotation keyframes
            }
            else
            {
                pJoint.Priority = Utils.BytesToInt(data, i); i += 4; // Joint Priority override?
                rotationkeys = Utils.BytesToInt(data, i); i += 4; // How many rotation keyframes
            }
            rotations = readKeys(data, ref i, rotationkeys, -1.0f, 1.0f);


            if (!BitConverter.IsLittleEndian)
            {
                positionkeys = Utils.BytesToInt(EndianSwap(data, i, 4)); i += 4; // How many position keyframes
            }
            else
            {
                positionkeys = Utils.BytesToInt(data, i); i += 4; // How many position keyframes
            }

            // Read in position keyframes
            positions = readKeys(data, ref i, positionkeys, -5f, 5f);

            pJoint.rotationkeys = rotations;
            pJoint.positionkeys = positions;

            return pJoint;
        }

        /// <summary>
        /// Read Keyframes of a certain type
        /// advance i
        /// </summary>
        /// <param name="data">Animation Byte array</param>
        /// <param name="i">Offset in the Byte Array.  Will be advanced</param>
        /// <param name="keycount">Number of Keyframes</param>
        /// <param name="min">Scaling Min to pass to the Uint16ToFloat method</param>
        /// <param name="max">Scaling Max to pass to the Uint16ToFloat method</param>
        /// <returns></returns>
        public binBVHJointKey[] readKeys(byte[] data, ref int i, int keycount, float min, float max)
        {
            float x;
            float y;
            float z;

            /*
                17          255  <-- Time Code
                17          255  <-- Time Code
                255         255  <-- X
                127         127  <-- X
                255         255  <-- Y
                127         127  <-- Y
                213         213  <-- Z
                142         142  <---Z

            */

            binBVHJointKey[] m_keys = new binBVHJointKey[keycount];
            for (int j = 0; j < keycount; j++)
            {
                binBVHJointKey pJKey = new binBVHJointKey();
                if (!BitConverter.IsLittleEndian)
                {
                    pJKey.time = Utils.UInt16ToFloat(EndianSwap(data, i, 2), 0, 0, Length); i += 2;
                    x = Utils.UInt16ToFloat(EndianSwap(data, i, 2), 0, min, max); i += 2;
                    y = Utils.UInt16ToFloat(EndianSwap(data, i, 2), 0, min, max); i += 2;
                    z = Utils.UInt16ToFloat(EndianSwap(data, i, 2), 0, min, max); i += 2;
                }
                else
                {
                    pJKey.time = Utils.UInt16ToFloat(data, i, 0, Length); i += 2;
                    x = Utils.UInt16ToFloat(data, i, min, max); i += 2;
                    y = Utils.UInt16ToFloat(data, i, min, max); i += 2;
                    z = Utils.UInt16ToFloat(data, i, min, max); i += 2;
                }
                pJKey.key_element = new Vector3(x, y, z);
                m_keys[j] = pJKey;
            }
            return m_keys;
        }
    }

    /// <summary>
    /// A Joint and it's associated meta data and keyframes
    /// </summary>
    public struct binBVHJoint
    {
        /// <summary>
        /// Name of the Joint.  Matches the avatar_skeleton.xml in client distros
        /// </summary>
        public string Name;

        /// <summary>
        /// Joint Animation Override?   Was the same as the Priority in testing.. 
        /// </summary>
        public int Priority;

        /// <summary>
        /// Array of Rotation Keyframes in order from earliest to latest
        /// </summary>
        public binBVHJointKey[] rotationkeys;

        /// <summary>
        /// Array of Position Keyframes in order from earliest to latest
        /// This seems to only be for the Pelvis?
        /// </summary>
        public binBVHJointKey[] positionkeys;
    }

    /// <summary>
    /// A Joint Keyframe.  This is either a position or a rotation.
    /// </summary>
    public struct binBVHJointKey
    {
        // Time in seconds for this keyframe.
        public float time;

        /// <summary>
        /// Either a Vector3 position or a Vector3 Euler rotation
        /// </summary>
        public Vector3 key_element;
    }

}
